Correlation of fluvial terraces and temporal steady-state incision on the onshore Makran accretionary wedge in southeastern Iran: Insight from channel profiles and 10Be exposure dating of strath terraces

Abstract

We describe and summarize the geomorphology of fl uvial terraces along the four major rivers draining the central, onshore Makran accretionary wedge in Iran, and describe uplifted marine terraces on the coast of this region. Thirty-fi ve strath terraces at different sites were dated using in situproduced cosmogenic 10 Be concentrations from surfaces and depth profi les. These new measurements reveal abandonment ages between ca. 15 and 380 ka. The age distribution allows determining the chronology of terrace levels and establishing regional correlations between two major regional levels. The geographically widespread correspondence suggests that these two levels result from a regional, climatically driven force. Systematic dating also provides evidence for time and spatial variations in incision rate, which enables distinguishing between a regionally uniform incision rate of 0.3-0.4 mm/a and higher local incision and/or uplift (~0.8 mm/a) rates. These spatial changes are consistent with where localized tectonic activity is recognized in the fi eld. We also dated, using 14 C in shells, four uplifted marine terraces on the coast of the study area. Comparing incision rates derived from strath terraces (0.3 mm/a) with published uplift estimates from marine terraces (0.2 mm/a) reveals that fl uvial rivers responded to a regional, long-term incision and surface uplift pattern. This rate refl ects the tectonically steady state of the wedge on a regional scale. Locally high incision rates delineate active faults and folds, indicating that perfect steady state is unlikely on short length scales.

Dating and morpho-stratigraphy of uplifted marine terraces in the Makran subduction zone (Iran)

“…Our current hypothesis to explain this discrepancy in kinematics is that the region undergoes N-S convergence during the interseismic period (i.e., now), whereas it experiences rare and brief episodes of N-S extension in response to large ruptures on the subduction interface. Similar coupling between compression and extension was observed following the 2011 Tohoku (Japan) megathrust earthquake (e.g., Hardebeck, 2012;Kato et al, 2011).…”

<sup>10</sup>Be depth profiles in glacial sediments on the Swiss Plateau: deposition age, denudation and (pseudo-) inheritance

“…However, the assumption of constant denudation is very likely wrong and would result in several meters of total denudation for MIS 6 sites and even several tens of meters for older sites. Total denudation of even more than 100 m is necessary to explain the 10 Be depth profiles in Deckenschotter (Häuselmann et al, 2007;Akçar et al, 2014;Claude et al, 2017). We suggest that denudational events related to periglacial dynamics might play an important role for the denudation history.…”

“…10 Be is produced by neutrogenic spallation and by muogenic interaction, mainly with oxygen (Gosse and Phillips, 2001;Heisinger et al, 2002a, b). In the last years, the application of 10 Be depth profiles has become an important method to date unconsolidated sediments (Hidy et al, 2010;Rixhon et al, 2011;Haghipour et al, 2014;Akçar et al, 2014;Delmas et al, 2015;Ruszkiczay-Rüdiger et al, 2016;Claude et al, 2017;Schaller et al, 2009). The advantage of this method is that it allows not only to calculate the age of the deposit but also denudation rate and the inherited share of 10 Be, accumulated in the catchment.…”

“…In situ produced 10 Be is produced at the Earth surface by cosmic radiation, and production decreases exponentially with depth (Gosse and Phillips, 2001). Until now, depth profile dating has mainly been applied to terraces and alluvial fans (Hidy et al, 2010;Rixhon et al, 2011;Haghipour et al, 2014;Akçar et al, 2014;Delmas et al, 2015;Ruszkiczay-Rüdiger et al, 2016;Claude et al, 2017;Schaller et al, 2009). In order to determine the deposition age of a moraine, one would generally sample large, stable erratic boulders for 10 Be surface exposure dating (Heyman et al, 2016).…”

Modelagem em Geografia Física: Teoria, Potencialidades e Desafios

“…Segundo estes autores, tais resultados sugerem que os topos convexos das encostas, inicialmente sugeridos como formas em equilíbrio (Gilbert, 1909), podem representar, em certas condições ambientais bem específicas, formas em estágio de quasi-equilíbrio. Espaço Aberto, PPGG -UFRJ, V. 6, N.1, p. 209-247, 2016ISSN 2237 Embora a discussão sobre a existência de formas em equilíbrio ainda persista na geomorfologia (Phillips, J.D., 1992;Whipple, 2001;Bracken e Wainwright, 2006;Phillips, 2011), vários trabalhos utilizando modelos e mensurações de campo comprovaram a existência de paisagens geomorfológicas em equilíbrio dinâmico (ou quasi) nas escalas de perfis de encostas (por ex., Ahnert, 1987;Fernandes e Dietrich, 1997), bacia de drenagem (por ex., Reneau e Dietrich, 1991), ou mesmo em áreas maiores, já em uma escala regional (por ex., Brunsden e Lin, 1991;Stolar et al, 2007;Cyr e Granger, 2008;Haghipour et al, 2015;Han et al, 2015). Esses trabalhos, de uma forma geral, inferem o alcance da condição de equilíbrio pela semelhança entre as taxas medidas (ou estimadas) de denudação e de soerguimento na região.…”